Currently, in the marketplace, there are available a wide variety of polishing and/or planarization devices and processes for producing semiconductor wafers. In the semiconductor manufacturing industry, it is often necessary for semiconductor wafers to be as close to uniform and planar, as the current methodology will allow. This is achieved by utilizing various devices and processes during the final grinding and polishing phases of the manufacturing process of semiconductor wafers wherein the wafer is polished to remove uneven surfaces, scratches and roughness. However, most of these conventional methods lead to distortions in the platen and thus result in an undesirable lack of uniformity of wafers, such as high thickness variation, taper, et cetera, following the lapping process.
In reviewing the prior art, there are a wide variety of wafer lapping devices and processes disclosed. Conventionally, a wafer lapping process in the semiconductor industry will utilize a device which will provide an upper pressurizing head or lapping plate, a lower lapping plate, a set of planetary gears, a plurality of wafer carriers, a wafer loader assembly, and a wafer unloader assembly. Generally these lapping plates polish and planarize the wafers by rotating clockwise or counterclockwise bearing upon the wafers loaded upon the wafer carriers. For example, the Hasegawa et al. U.S. Pat. No. 5,174,067 discloses a typical wafer lapping apparatus that also utilizes a pair of turntable stages where each has a vertical central shaft and a pin where the wafer carriers are piled upon. Further, the Hashimoto U.S. Pat. No. 5,333,413 discloses a typical automatic wafer lapping apparatus wherein the wafer lapping apparatus further includes a position sensor for detecting the position of the wafer carriers and a device for cleaning the wafer holder. Similarly, the Nakamura U.S. Pat. No. 5,361,545 discloses a polishing device wherein four polishing devices are linearly arranged and provide arm shafts capable of moving in the longitudinal direction wherein wafers may be moved between a discharge position upon a polishing plate and a specified position outside the polishing plate.
The Kifta U.S. Pat. No. 5,647,789, also discloses a polishing machine having a plurality of carriers and method which includes a polishing disc that rotates first in one direction, and then in a reverse direction, in order to more effectively spread slurry and optimize planarization. It is also provided with a pair of guide rollers for pinching a holding member. Similarly, the Greenlaw U.S. Pat. No. 5,697,832 discloses a planetary grinding or polishing machine wherein an outer ring gear, upper platen and lower platen are independently rotatable in a clockwise or counterclockwise position.
The Leach U.S. Pat. No. 5,733,175 also discloses a polishing apparatus having rotatable plates wherein the polishing plate and workpiece plate rotate at a constant rate relative to each other. This device has two overlapping platens, one holds a workpiece while the other holds a polishing pad and rotates in the same direction, either clockwise or counterclockwise.
In Sandhu U.S. Pat. No. 5,762,537 a system is disclosed for polishing a semiconductor wafer having means for heating a wafer while it is being polished by a polishing head and means to apply pressure where desired. A processor is provided which can control both the processing rate and pressure upon the workpiece.
Further, the Kim U.S. Pat. No. 5,951,380 discloses a polishing method and apparatus that utilizes different polishing materials on a single pad to control the polishing characteristics, while the Nagahara U.S. Pat. No. 6,004,193 discloses a polishing apparatus that employs a retainer ring which retains a semiconductor wafer against the polishing pad while it also conditions the pad during wafer polishing or any substrate.
In the semiconducting industry, wafers are generally polished by being pressed between two rotatable plates. The Yang U.S. Pat. No. 6,054,017 discloses a polishing apparatus where a wafer is pressed between a polishing head and polishing pad which are both rotatable. Similarly, the Arai U.S. Pat. No. 6,074,277 discloses a polishing apparatus with a rotating plate, but this plate comprises an inner peripheral portion and a donut-shaped outer portion that may rotate independently of one another in opposite directions at controlled speeds to make the wear of the polishing pad and the inner plate substantially equal.
Further, the Kotagiri U.S. Pat. No. 6,080,048 discloses a polishing machine that has a carrier providing through-holes to accommodate wafers which are pinched between two polishing plates and has both sides polished by a driver mechanism that moves the carrier along a circular orbit without revolving.
The Perlov U.S. Pat. No. 6,086,457 discloses an apparatus and method for transferring wafers between polishing heads and washer stations. Robotics are used to transfer the wafers during processing and multiple heads are utilized to improve performance.
The Sandhu U.S. Pat. No. 6,120,347 discloses a system which includes a polishing assembly having a polishing plate, a wafer carrier, and a controller to adjust polishing parameters such as polishing rates, polishing pressure and positioning.
The Deuscher U.S. Pat. No. 6,120,352 discloses a method of lapping or polishing using an adjustable flat surface and abrasive sheets, wherein gaseous pressure is reduced between the back of the abrasive sheet and the platen. Further, in the Duescher U.S. Pat. No. 6,149,506, this reference discloses a method and apparatus for high speed lapping with a rotatable platen having an abrasive surface, a moveable work piece holder, and a flexible shaft which are cable of polishing at extremely high speeds. This reference also discloses the use of a work piece holder as a segment of a spherical element, a cylindrical housing and a gimbal mechanism. A vacuum is used to secure the workpiece. Duescher, U.S. Pat. No. 6,769,969 B1 also discloses raised island abrasive sheet materials containing a thin coating of diamond particles, and a method for using the abrasive sheeting during a high speed lapping process.
The Nystrom U.S. Pat. No. 6,152,806 discloses a chemical mechanical polishing (“CMP”) apparatus with concentric platens that can be rotated independently of each other in either a clockwise or counterclockwise direction. A polishing pad is attached to each platen.
The Mitsuhashi U.S. Pat. No. 6,168,684 B1 discloses a wafer polishing method and apparatus which has a rotary polishing bed, an abrasive cloth, a rotary driver for the wafer, and a grooved retaining ring. The polishing slurry is dispensed in a direction opposite that of the polishing pad.
The Sandhu U.S. Pat. No. 6,338,667 B2 discloses a system for real-time control of a semiconductor polishing process having a plate, a wafer carrier and a control which may travel in linear or nonlinear polishing paths. It is also provided with a processor to control rotational velocity of both platen and wafer, the wafer speed across the platen, the pressure exerted on the wafer, slurry composition, flow rate and temperature of a wafer surface.
The Halley U.S. Pat. No. 6,346,036 B1 discloses a polishing system with a movable polishing head and dual magazine regions where substrate complexes are placed. Further, the Berman U.S. Pat. No. 6,375,550 B1 discloses an apparatus which has a wafer carrier assembly that is configured to apply pressure to the wafer at two different sets of predetermined positions. The Huynh U.S. Pat. No. 6,432,823 B1 discloses a system of using at least two platens in an off-concentric position to polish a single wafer simultaneously.
The Easter U.S. Pat. No. 6,537,135 B1 discloses a polishing method and apparatus which moves the holding device in a substantially curvilinear path relative to the polishing surface, which curvilinear path preferably comprises a figure eight. Furthermore, the Tolles U.S. Pat. No. 6,575,825 B2 discloses a polishing pad with passageways therethrough which vent to the atmosphere, as they may comprise a variety of groove configurations.
The Halley U.S. Pat. No. 6,629,874 B1 discloses a method for adjusting polishing parameters by using contemporaneous height measurements of the surface of the wafer by reflecting light thereupon.
The Zimmer U.S. Pat. No. 6,632,127 discloses a polishing pad conditioning head with a substrate and a layer of fine-grain chemical vapor deposited polycrystalline diamond bonded to the substrate for crystalline growth thereupon.
The Vogtmann U.S. Pat. No. 6,672,943 B2 discloses an eccentric or elliptical abrasive wheel which interacts with a spindle adapted to hold a wafer to prevent overgrind of the workpiece. An elliptical or oval shaped matrix is utilized to accomplish this purpose.
The Ficarro U.S. Pat. No. 6,702,657 B2 discloses a polishing machine having multiple carriers which are rotated around a vertical axis with roller pairs. Further, the Chadda U.S. Pat. No. 6,793,565 B1 discloses an apparatus with at least two carousels which rotate to polish a workpiece. It also discloses the use of a polishing web with a face.
The Halley U.S. Pat. No. 6,855,030 B2 discloses a method of performing a planarization process using an apparatus having a docking station where one may remove a module while other modules are still being processed. Each module may be independently controlled by separate carriers.
The Moloney U.S. Pat. No. 7,004,822 discloses a polishing method which is based on differing rotation of a pad dresser, head, and/or polishing head in order to increase center removal profile. It also utilizes orbital and spin action during CMP.
The Ina U.S. Pat. No. 7,081,038 B2 discloses a polishing method of polishing a substrate where the substrate and the pad are rotated first in one direction, then in a second direction opposite to the first direction.
The Hidaka U.S. Pat. No. 7,102,206 B2 discloses a semiconductor having a notched edge portion, and a method for making for making the notch and for reducing edge step formation during CMP.
The Kennedy U.S. Pat. No. 7,104,871 B1 discloses a method for resurfacing a compact disc where the disc and the abrasive material are rotated in opposite directions.
The Chen U.S. Pat. No. 7,166,016 B1 discloses a six headed carousel with substrate heads which align with four polishing stations and two load cups with head portions. Each head is configured to support and transfer a substrate.
The Novak U.S. Pat. No. 7,172,493 B2 discloses a polishing apparatus having actuators which rotate the polishing assembly and apply force to the workpiece. The actuators also cooperate to adjust the pressure of the polishing pad.
The Jeong U.S. Pat. No. 7,186,165 B2 discloses a semiconductor wafer polishing apparatus which may be configured to continuously polish wafers while other wafers are being transferred to different positions. It discloses four wafer carriers and the device further has a small footprint.
The Large U.S. Pat. Pub. No. 2002/0049029 A1 discloses a CMP machine with a spindle coupled to a wafer carrier which is capable of producing microscopic vibrations during the lapping process via a piezoelectric drive.
The Sasaki U.S. Pat. Pub. No. 2001/0029158 A1 discloses a polishing apparatus with a plurality of polishing portions and a cleaning portion. Furthermore, the Ivanov U.S. Pat. Pub. No. 2006/0030157 A1 discloses a method and apparatus for processing microelectronic topographies which include a substrate holder or microelectronic topography which rotates to expose these to a fluid.
The Jeong U.S. Pat. Pub. No. 2006/0105680 A1 discloses an apparatus and method for loading and unloading semiconductor wafers on multiple wafer carriers for continual processing, thereby reducing idle processing time.
The Chandrasekaran U.S. Pat. Pub. No. 2007/0049179 A1 discloses retaining rings and associated planarizing apparatuses which can be positioned on a carrier head. It also discloses the use of grooves in the base surface.
Thus, nowhere in the prior is seen a polishing method where pairs of polishing heads rotating counterclockwise and pairs of heads rotating clockwise are counterbalanced throughout the polishing process in combination with the use of concentric conditioning rings in order to provide improved continuous and controllable planarization resulting in high throughput of premium quality, consistent, ultra-flat wafers by means of maintaining reduced distortion of the lapping platen during processing.